White Nose Syndrome threatens local bat colony

August 13, 2012

WEST GREENWICH - The Woodville Barn at the University of Rhode Island W. Alton Jones Campus has been the spring and summer home for a thriving maternal colony of little brown bats for a very long time. Every March or April, the same colony returns to roost in the barn for the warmer months, and each member of the colony, which is females only, returns from its far away hibernation ready to bear one pup. It is a truly fascinating life cycle.

However, this particular colony of little brown bats (Myotis Lucifigus), and the species as a whole, is currently in the midst of a catastrophic decline in population. According to URI Professor Peter August, who has been studying this bat colony for 30 years, what was once the most common bat in Rhode Island, and the northeast, is now a bat in peril.

As recently as 2006, little brown bat colonies in the northeast began showing signs of decline. At the Woodville Barn, what was a population of approximately 150 bats every single year began drop in 2009. As of Today, less than 50 bats, mothers and pups, live in the barn.

Scientists have determined that the cause of the precipitous decline in numbers can be attributed to a fungus, which leads to something called White Nose Syndrome in the small winged mammals. Admittedly, August and scientific colleagues had never heard of such a thing until it started killing off the bats they studied.

"I don't think anyone in North America had even heard the words White Nose Syndrome until the mid to late two thousands," August said. "This is all very new."

White Nose Syndrome severely disrupts a pattern that has characterized the lives of little brown bats for as long as science can recall. Each fall, countless numbers of the species return to caves and mines in New Hampshire, Vermont and upstate New York to spend the winter huddled together in a deep sleep. When they first arrive, it is the only time that adult male and adult female little brown bats are together, so as nature would have it, they mate.

During the long hibernation, the females store the males' portion of the reproductive formula, and when they awake in the spring, the immediately do two things: ovulate and fly. They travel all they way back to their colonies' roosting spots, like the Woodville Barn, and they arrive pregnant. The males, however, live a life of solitude, feeding on bugs in the woods.

Each female bat will give birth to exactly one pup around June of each year. While nursing their pups, the mother bats will leave the roost when the sun sets to go out and feed. Each little bat, which has a wingspan of not much more than six inches, can consume about 1,000 mosquitoes per night, much to the benefit of campers at W. Alton Jones summer camp.

The babies eventually learn to fly and feed themselves, and somehow, learn how to get back to the same caves their mothers do when September rolls around. Only one out of 10 of the young bats will survive their first winter though, as they simply had not mastered bug-catching well enough to store the amount of fat needed to survive a winter-long slumber.

Even though the infant mortality rate is so high, the bat population maintains itself because little brown bats can live up to 30 years, giving the ones that survive plenty of opportunities to reproduce.

White Nose Syndrome has made this long-sustainable life cycle very difficult on the bats. The fungus irritates them as they sleep in the caves, causing them to wake up. When they wake, they fly around and groom, rapidly wasting precious stored energy. When this happens, they simply do not have enough left in their tiny bodies to survive the winter.

August said that the fungus is common in Europe, where the bats have grown immune to it, but American bat populations have no natural defense for the fungus, which is completely new to them. Scientists still do not understand the physiology of the fungus, and according to August, once a cave harbors a just a few bats that have been exposed to it, the mortality rate can be astronomical.

August talked about the substantial ecological impact the declining bat population can have, specifically that there are less of them around to control the populations of mosquitoes and insects that can be harmful to crops.

"The big picture reflection that I have on this is that catastrophic events to species and ecosystems can happen fast," August said. However, the professor said that there is a positive way to look at this daunting situation.

"What we are seeing is evolution and natural selection right before our very eyes," he said. "While the little brown bat populations have suffered a precipitous decline, these bats in the barn right now have survived it. In 100 years, the population will recover, and what is 100 years on the scale of evolution? Nothing. A wink. A blip on the radar screen."

So while children from the summer camp gather near the Woodville Barn as the sun sets behind them to catch a glimpse of bats swooping out of the barn and jetting off into the night, Prof. August knows that while this particular colony has decreased 4-fold in just three years, natural will play itself out, the bats will adapt, and the bats will survive.

"Species and ecosystems have a resiliency that sometimes we fail to appreciate," he said.